Radiation therapy of the oral cavity results in a gustatory disorder known as post-irradiation gustatory dysfunction (PIGD). although previous studies on animals have revealed a profound loss of taste buds 7-10 days following irradiation, the time course of gustatory loss in patients (2-3 days) does not correlate with the gross disappearance of taste buds. The proposed pilot experiments attempt to develop a small animal model of PIGD embracing both behavioral and morphological assessments of loss. The behavioral measure of taste abilities will be by means of a two-bottle preference test. Taste stimuli to be used in different populations of animals are quinine (0.0125%) and two concentrations of salt -- 0.6%, a preferred taste, and 1.8% an avoided taste. Further, use of specific immunological and lectin probes will permit evaluation of which cell populations or nerve fibers exhibit the earliest signs of change following irradiation. The probes used selectively recognize dark cells, light- intermediate taste cells, intragemmal nerve fibers, peptidergic nerve fibers and developing taste cells. Whether changes in any of these tissue elements correlates with the behavioral changes following irradiation should be discernable. Once the animal model system has been established, a full research project involving measurement on basal cell turnover and cell cycle rates will be feasible as will correlative studies on patient populations.